Uncommonly isolated clinical Pseudomonas: identification and phylogenetic assignation

Yearlong analysis of bacterial diversity in hospital sink drains: culturomics, antibiotic resistance and implications for infection control

Hospitals can carry high levels of bacterial diversity from all types of origins, such as human skin, outside environment and medical equipment. Sink drains in clinical settings are considered reservoirs for pathogenic bacteria and potential sources of hospital-acquired infections (HAI's) and antibiotic resistance genes (ARGs). Therefore, infection control measures are crucial to minimizing the risks associated with these reservoirs. Recent research has focused primarily on intensive care units (ICUs) and known pathogens, often employing metagenomic approaches that do not include bacterial isolation. This study aims to evaluate bacterial diversity using culturomics, extending the investigation beyond the ICU to identify antibiotic-resistant bacteria. A total of four samplings were conducted over 1 year (March 2022 to March 2023) in five different hospital wards [ICU, General Medicine (GM), Hematology (H), Short stay unit (UCE), and Microbiology laboratory (MS)]. All samples were cultured on selective and non-selective culture media, resulting in 1,058 isolates identified using MALDI-TOF MS, with a subset confirmed through 16S rRNA gene sequencing. Isolates retrieved from antibiotic supplemented agar were subjected to antibiotic susceptibility testing. The highest bacterial diversity, as measured by the Shannon index, was observed in the ICU and GM wards, posing significant risks to patients in these areas. While bacterial genera were largely similar across wards and sampling times, with Pseudomonas and Stenotrophomonas being the most prevalent, different species were detected in each sampling, indicating no loss of diversity. This suggests that these environments undergo dynamic changes over time, influenced by their surroundings. The results also indicate a relationship between human activity and drain usage and the presence of Pseudomonas aeruginosa, the most commonly found species across most wards. Antibiotic susceptibility testing revealed that all tested isolates, except for one, were multi-resistant, including clinically relevant species, such as P. aeruginosa and K. pneumoniae. Hospital drains may serve as reservoirs for both known and emerging pathogens exhibiting high antibiotic resistance phenotypes. Their dynamic nature may provide insights into strategies for preventing the colonization of these environments by such species.

Comamonas resistens sp. nov. and Pseudomonas triclosanedens sp. nov., two members of the phylum Pseudomonadota isolated from the wastewater treatment system of a pharmaceutical factory

Five strains of two novel species were isolated from the wastewater treatment systems of a pharmaceutical factory located in Zhejiang province, PR China. Strains ZM22T and Y6 were identified as belonging to a potential novel species of the genus Comamonas, whereas strains ZM23T, ZM24 and ZM25 were identified as belonging to a novel species of the genus Pseudomonas. These strains were characterized by polyphasic approaches including 16S rRNA gene analysis, multi-locus sequence analysis, average nucleotide identity (ANI), in silico DNA-DNA hybridization (isDDH), physiological and biochemical tests, as well as chemotaxonomic analysis. Genome-based phylogenetic analysis further confirmed that strains ZM22T and Y6 form a distinct clade closely related to Comamonas testosteroni ATCC 11996T and Comamonas thiooxydans DSM 17888T. Strains ZM23T, ZM24 and ZM25 were grouped as a separate clade closely related to Pseudomonas nitroreducens DSM 14399T and Pseudomonas nicosulfuronedens LAM1902T. The orthoANI and isDDH results indicated that strains ZM22T and Y6 belong to the same species. In addition, genomic DNA fingerprinting demonstrated that these strains do not originate from a single clone. The same results were observed for strains ZM23T, ZM24 and ZM25. Strains ZM22T and Y6 were resistant to multiple antibiotics, whereas strains ZM23T, ZM24 and ZM25 were able to degrade an emerging pollutant, triclosan. The phylogenetic, physiological and biochemical characteristics, as well as chemotaxonomy, allowed these strains to be distinguished from their genus, and we therefore propose the names Comamonas resistens sp. nov. (type strain ZM22=MCCC 1K08496T=KCTC 82561T) and Pseudomonas triclosanedens sp. nov. (type strain ZM23T=MCCC 1K08497T=JCM 36056T), respectively.

Comparative genomics of Stutzerimonas balearica (Pseudomonas balearica): diversity, habitats, and biodegradation of aromatic compounds

Stutzerimonas balearica (Pseudomonas balearica) has been found principally in oil-polluted environments. The capability of S. balearica to thrive from the degradation of pollutant compounds makes it a species of interest for potential bioremediation applications. However, little has been reported about the diversity of S. balearica. In this study, genome sequences of S. balearica strains from different origins were analyzed, revealing that it is a diverse species with an open pan-genome that will continue revealing new genes and functionalities as the genomes of more strains are sequenced. The nucleotide signatures and intra- and inter-species variation of the 16S rRNA genes of S. balearica were reevaluated. A strategy of screening 16S rRNA gene sequences in public databases enabled the detection of 158 additional strains, of which only 23% were described as S. balearica. The species was detected from a wide range of environments, although mostly from aquatic and polluted environments, predominantly related to petroleum oil. Genomic and phenotypic analyses confirmed that S. balearica possesses varied inherent capabilities for aromatic compounds degradation. This study increases the knowledge of the biology and diversity of S. balearica and will serve as a basis for future work with the species.

Pseudomonas arcuscaelestis sp. nov., isolated from rainbow trout and water

Cells of strains P66^T, V1 and W15Feb18 are Gram-stain-negative short rods and motile by one polar flagellum. Strain P66^T was isolated from rainbow trout (Oncorhynchus mykiss) cultivated at a fish farm in Turkey. Strain V1 was isolated from sand of an intertidal shore on the Galicia coast in Spain and strain W15Feb18 was isolated from water collected at the Woluwe River in Belgium. Based on 16S rRNA sequence similarity values, the strains were grouped under the genus Pseudomonas and the Pseudomonas putida phylogenetic group of species. The DNA G+C content ranged from 58.5 to 58.9 mol%. The strains were characterized phenotypically by the API 20NE and Biolog GEN III tests, and chemotaxonomically by their whole-cell MALDI-TOF MS protein profiles and fatty acid contents. The absence of the hydrolysis of gelatin and the assimilation of arabinose, mannose and mannitol differentiated these strains from the closest species, Pseudomonas alkylphenolica. The major fatty acid components were C_16:0 (29.91-31.68 %) and summed feature 3 (36.44-37.55 %). Multilocus sequence analysis with four and 83 housekeeping gene sequences and a core proteome analysis showed that these strains formed a phylogenetic cluster in the P. putida group of species. Genome comparisons by the average nucleotide identity based on blast and the Genome-to-Genome Distance Calculator demonstrated that the three strains belonged to the same genomic species and were distant from any known species, with similarity values lower than the thresholds established for species in the genus Pseudomonas. These data permitted us to conclude that strains P66^T, V1 and W15Feb18 belong to a novel species in the genus Pseudomonas, for which the name Pseudomonas arcuscaelestis sp. nov. is proposed. The type strain is P66^T (=CECT 30176^T=CCUG 74872^T). The other strains have been deposited in the CECT with the corresponding collection numbers: V1 (=CECT 30356) and W15Feb18 (=CECT 30355).

Pseudomonas lalucatii sp. nov. isolated from Vallgornera, a karstic cave in Mallorca, Western Mediterranean

Caves are extreme underground environments colonized by oligotrophic bacterial communities that influence mineral transformations. The identification at the species level is important and this study aims to the taxonomic characterisation of four bacterial strains previously isolated from rock surfaces and water samples from a karstic cave located on Mallorca (Spain) that were assigned to the genus Pseudomonas according to 16S rRNA nucleotide sequence analysis. Sequence analysis of the RNA polymerase sigma factor gene (rpoD) allocated these strains to the P. fluorescens lineage within the P. anguilliseptica phylogenetic group, close to the P. benzenivorans type strain. A polyphasic taxonomic approach included phenotypic characterization, fatty acid composition analysis, and whole-cell protein profiling, together with phylogenomic data. The results supported the proposal of a new species in the Pseudomonas genus. Characteristic fatty acid methyl esters of members of the Pseudomonas genus were present (C16:0, C10:0 3-OH, C12:0 2-OH and C12:0 3-OH) and the C12:1 3OH content differentiated these strains from P. benzenivorans. The genomic G + C mol% content of the four sequenced genomes was 66.9%. The average nucleotide indices based on BLAST analysis and the calculation of genome-to-genome distance with respect to their closest relative were lower than 88% and 30%, respectively. These data confirm that the four isolates, R1b-4, R1b-52A, A2bC-1 and R1b-54^T, represent a new species, for which the name Pseudomonas lalucatii is proposed, with strain R1b-54^T as the type strain (=CCUG 74754^T = CECT 30179^T). This is the first species in the P. anguilliseptica group isolated from this extreme habitat.

Pseudomonas anatoliensis sp. nov and Pseudomonas iridis sp. nov. isolated from fish

In a study carried out between 2013 and 2018 in fish farms in Turkey, several putative novel species were isolated. The 16S rRNA nucleotide sequences of fourteen strains of Gram-negative rods, which were isolated from asymptomatic and symptomatic rainbow trouts (Onchorhynchus mykiss), placed them under the genus Pseudomonas. The similarity values of the concatenated nucleotide sequences of the rpoD, rpoB, gyrB and 16S rRNA genes clustered these isolates into the P. fluorescens phylogenetic group of species and into the Pseudomonas koreensis subgroup, close to Pseudomonas helmanticensis and Pseudomonas baetica. An isolate of a totally different origin, strain CCUG 67011, clustered with these isolates. Phenotypic characterization, together with the chemotaxonomic data, whole-cell MALDI-TOF MS and fatty acids methyl esters analyses were performed. The DNA G + C content was 58.7 mol% for isolate P9^T and 58.8 mol% for isolate P42^T. The phylogenomic analysis and whole genome nucleotide sequences of four of these isolates confirmed that the isolates P9^T, P25 and P141, represent a novel species for which the name Pseudomonas anatoliensis sp. nov. is proposed, with P9^T as the type strain (=CCUG 74755^T = CECT 3172^T). The isolates P1, P2, P10, P27, P30, P24a, P42^T, P117, P139, P152 and CCUG 67011 represent another novel sècies, for which the name Pseudomonas iridis sp. nov. is proposed, with P42^T as the type strain (=CCUG 74870^T = CECT 3174^T).

Summary of Novel Bacterial Isolates Derived from Human Clinical Specimens and Nomenclature Revisions Published in 2018 and 2019

Knowledge of novel prokaryotic taxon discovery and nomenclature revisions is of importance to clinical microbiology laboratory practice, infectious disease epidemiology, and studies of microbial pathogenesis. Relative to bacterial isolates derived from human clinical specimens, we present an in-depth summary of novel taxonomic designations and revisions to prokaryotic taxonomy that were published in 2018 and 2019. Included are several changes pertinent to former designations of or within Propionibacterium spp., Corynebacterium spp., Clostridium spp., Mycoplasma spp., Methylobacterium spp., and Enterobacteriaceae Future efforts to ascertain clinical relevance for many of these changes may be augmented by a document development committee that has been appointed by the Clinical and Laboratory Standards Institute.

Diversity of pathogenic Pseudomonas isolated from citrus in Tunisia

The damages observed in Tunisian citrus orchards have prompted studies on the Pseudomonas spp. responsible for blast and black pit. Prospective orchards between 2015 and 2017 showed that the diseases rapidly spread geographically and to new cultivars. A screening of Pseudomonas spp. isolated from symptomatic trees revealed their wide diversity according to phylogenetic analysis of their housekeeping rpoD and cts genes. The majority of strains were affiliated to Pseudomonas syringae pv. syringae (Phylogroup PG02b), previously described in Tunisia. However, they exhibited various BOX-PCR fingerprints and were not clonal. This work demonstrated, for the first time in Tunisia, the involvement of Pseudomonas cerasi (PG02a) and Pseudomonas congelans (PG02c). The latter did not show significant pathogenicity on citrus, but was pathogenic on cantaloupe and active for ice nucleation that could play a role in the disease. A comparative phylogenetic study of citrus pathogens from Iran, Montenegro and Tunisia revealed that P. syringae (PG02b) strains are closely related but again not clonal. Interestingly P. cerasi (PG02a) was isolated in two countries and seems to outspread. However, its role in the diseases is not fully understood and it should be monitored in future studies. The diversity of pathogenic Pseudomonas spp. and the extension of the diseases highlight that they have become complex and synergistic. It opens questions about which factors favor diseases and how to fight against them efficiently and with sustainable means.

High-quality draft genome sequences of Pseudomonas monteilii DSM 14164T, Pseudomonas mosselii DSM 17497T, Pseudomonas plecoglossicida DSM 15088T, Pseudomonas taiwanensis DSM 21245T and Pseudomonas vranovensis DSM 16006T: taxonomic considerations

Pseudomonas is the bacterial genus of Gram-negative bacteria with the highest number of recognized species. It is divided phylogenetically into three lineages and at least 11 groups of species. The Pseudomonas putida group of species is one of the most versatile and best studied. It comprises 15 species with validly published names. As a part of the Genomic Encyclopedia of Bacteria and Archaea (GEBA) project, we present the genome sequences of the type strains of five species included in this group: Pseudomonas monteilii (DSM 14164^T), Pseudomonas mosselii (DSM 17497^T), Pseudomonas plecoglossicida (DSM 15088^T), Pseudomonas taiwanensis (DSM 21245^T) and Pseudomonas vranovensis (DSM 16006^T). These strains represent species of environmental and also of clinical interest due to their pathogenic properties against humans and animals. Some strains of these species promote plant growth or act as plant pathogens. Their genome sizes are among the largest in the group, ranging from 5.3 to 6.3 Mbp. In addition, the genome sequences of the type strains in the Pseudomonas taxonomy were analysed via genome-wide taxonomic comparisons of ANIb, gANI and GGDC values among 130 Pseudomonas strains classified within the group. The results demonstrate that at least 36 genomic species can be delineated within the P. putida phylogenetic group of species.

Pseudomonas sivasensis sp. nov. isolated from farm fisheries in Turkey

A study of 91 isolates from fish farms in Turkey showed that isolates P7^T, P11, P24b, P29, P72, P73 and P158 belonged to the genus Pseudomonas according to 16S rRNA nucleotide sequence analysis. The analysis of the sequences of the RNA polymerase sigma factor gene (rpoD) located these strains in the Pseudomonas fluorescens lineage of species within the P. fluorescens subgroup, close to the cluster composed of the species Pseudomonas grimontii, Pseudomonas marginalis and Pseudomonas panacis. Based on similarities in the 16S rRNA and rpoD gene sequences of three previously isolated strains from other origins (CCUG 57209, CCUG 62357 and W5.2-93) linked them to the same cluster. A polyphasic taxonomic approach including phenotypic characterization, fatty acid composition, and multilocus sequence analysis, together with whole-cell MALDI-TOF data, corroborated this assumption. The genome G+C mol% contents were 59.48 and 59.71, respectively. The average nucleotide indices based on BLAST analysis and the genome-to-genome distance calculation for the P7^T and CCUG 57209 strains with their closest relative, P. grimontii, were 88.16-88.29% and 38.10-38.20%, respectively. These data confirm that isolates P7^T, P11, P24b, P29, P72, P73, P158, CCUG 57209, CCUG 62357 and W5.2-93 represent a new species for which the name Pseudomonas sivasensis is proposed, with P7^T as a type strain (=CCUG 74260^T= and CECT30107^T).

Genomics in Bacterial Taxonomy: Impact on the Genus Pseudomonas

The introduction of genomics is profoundly changing current bacterial taxonomy. Phylogenomics provides accurate methods for delineating species and allows us to infer the phylogeny of higher taxonomic ranks as well as those at the subspecies level. We present as a model the currently accepted taxonomy of the genus Pseudomonas and how it can be modified when new taxonomic methodologies are applied. A phylogeny of the species in the genus deduced from analyses of gene sequences or by whole genome comparison with different algorithms allows three main conclusions: (i) several named species are synonymous and have to be reorganized in a single genomic species; (ii) many strains assigned to known species have to be proposed as new genomic species within the genus; and (iii) the main phylogenetic groups defined by 4-, 100- and 120-gene multilocus sequence analyses are concordant with the groupings in the whole genome analyses. Moreover, the boundaries of the genus Pseudomonas are also discussed based on phylogenomic analyses in relation to other genera in the family Pseudomonadaceae. The new technologies will result in a substantial increase in the number of species and probably split the current genus into several genera or subgenera, although these classifications have to be supported by a polyphasic taxonomic approach.

The applicability of gene sequencing and MALDI-TOF to identify less common gram-negative rods (Advenella, Castellaniella, Kaistia, Pusillimonas and Sphingobacterium) from environmental isolates

Our aim was to identify less common non-fermenting gram-negative rods during the bioremediation process. Five genera were found: Advenella, Castellaniella, Kaistia, Pusillimonas and Sphingobacterium, for a total of 15 isolates. Therefore, we evaluated the applicability of four methods currently available for bacteria identification: (1) conventional biochemical methods, (2) the VITEK^®-2 system, (3) MALDI-TOF mass spectrometry and (4) 16S rRNA gene sequencing. The biochemical methods and the VITEK^®-2 system were reliable only for the Sphingobacterium isolate and solely at the genus level. Both MALDI-TOF mass spectrometry platforms (Bruker and VITEK^® MS) did not achieve reliable identification results for any of these genera. 16S rRNA gene sequencing identified eight isolates to the species level but not to the subspecies level, when applicable. The remaining seven isolates were reliably identified through 16S rRNA gene sequencing to the genus level only. Our findings suggest that the detection and identification of less common genera (and species) that appeared at certain moments during the bioremediation process can be a challenge to microbiologists considering the most used techniques. In addition, more studies are required to confirm our results.

The first report of Pseudomonas oryzihabitansin infection in a patient with hidradenitis suppurativa

Hidradenitis suppurativa (HS) is one of the neglected chronic inflammatory disorders which has not efficient treatment. These patients were susceptible to various infectious diseases because of their changes in immuneresponse. Also, HS pathogenesis remains unclear and its report can create novel insight into mechanism and pathogenesis of this infection. Moreover, given that different susceptibility patterns of Pseudomonas spp this species should be identified to the species level; molecular methods are rapid, inexpensive, and reliable method for identification of infectious agents to the species level and appropriate treatment of infections.

New species of pathogenic Pseudomonas isolated from citrus in Tunisia: Proposal of Pseudomonas kairouanensis sp. nov. and Pseudomonas nabeulensis sp. nov

A collection of Pseudomonas strains was isolated in different regions of Tunisia in the period 2016-2017 from the fruits and leaves of Citrus sinensis cv. 'Valencia Late' and Citrus limon cv. 'Eureka' plants with symptoms of blast and black pit disease. A phylogenetic analysis of the housekeeping gene rpoD was used for strain identification at the species level. The results demonstrated the affiliation of these strains with the genus Pseudomonas and revealed the presence of 11 strains representing two putative new species in two monophyletic branches. These strains were analyzed morphologically and genotypically by multilocus sequence analyses of the rpoD, gyrB and 16S rRNA (rrs) gene sequences, and their phenotypic characteristics by API 20NE and Biolog GEN III. Plant pathogenic properties were confirmed on fruits and detached leaves of C. limon cv. 'Eureka'. Fatty acids and WC MALDI-TOF MS major protein profiles were determined. The genomes of both representatives were sequenced. The average nucleotide index and genome-to-genome distance from KC12^T and E10B^T are below the cut-off established for a described species. These results support the conclusion that the strains KC12^T, KC17, KC20, KC22, KC24A, KC25 and KC26 represent a novel species of Pseudomonas, for which the name of Pseudomonas kairouanensis is proposed. The type strain is KC12^T (=CECT9766 and CFBP 8662). The strains E10B^T, E10AB, E10CB1 and Iy3BA represent another novel species of Pseudomonas for which the name of Pseudomonas nabeulensis is proposed; the type strain is E10B^T (=CECT9765 and CFBP 8661).

The current status on the taxonomy of Pseudomonas revisited: An update

The genus Pseudomonas described in 1894 is one of the most diverse and ubiquitous bacterial genera which encompass species isolated worldwide. In the last years more than 70 new species have been described, which were isolated from different environments, including soil, water, sediments, air, animals, plants, fungi, algae, compost, human and animal related sources. Some of these species have been isolated in extreme environments, such as Antarctica or Atacama desert, and from contaminated water or soil. Also, some species recently described are plant or animal pathogens. In this review, we revised the current status of the taxonomy of genus Pseudomonas and the methodologies currently used for the description of novel species which includes, in addition to the classic ones, new methodologies such as MALDI-TOF MS, MLSA and genome analyses. The novel Pseudomonas species described in the last years are listed, together with the available genome sequences of the type strains of Pseudomonas species present in different databases.